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The effect of commercial thinning in Scots pine stands on the growth of black cherry
Abstract Black cherry (Prunus serotina Ehrh.) is one of the most abundant invasive species found in Polish forests. The mass occurrence of this species in pine stands is one of the main problems of silviculture. Therefore, the paper addresses the problem of the effect of commercial thinning, which increases the access of light to the lower layers of the stand, on the annual growth of rings and the development of black cherry. The study attempted to determine the strength of the progression of the black cherry threat as expressed by increased diameter increment. It was assumed that the thickness increment of mature black cherry individuals after thinning would be significantly greater compared to the average thickness increment before thinning. Over time after the treatment, the average growth of sprouts of black cherry will decrease. Six pine stands differing in age and timing of the silvicultural treatment in the Golub–Dobrzyn Forest District (N 57°81′42″ E 50°20′19″) were analysed. A positive effect of commercial thinning on the thickness increment of black cherry was found in all the studied plots. Over time, the average increment of black cherries resulting from the clearance decreased. Conducting late thinning, in pine stands where black cherry occurs, results in an increased threat of its expansion. To limit the development of black cherry at this stage of pine stand management, two solutions are possible. The first is to abandon late thinning or reduce the intensity of the treatment, which will inhibit its rapid expansion. The second scenario is to limit the occurrence of black cherry a few years before thinning, perform thinning and introduce understorey or underplanting from native competitive tree species.